Why do car batteries die so fast if you leave a light on in the car but the car is not running?

Question

Why dont they die while you drive and everything is on

Answer 1

In a car, the battery is continously charged while the engine is on, by an alternator.

The alternator is the belt in front of your engine, that keeps running when the engine is on.

If your engine is off, the alternator will not be charging the battery, and thus, your battery is "flying on a dead stick". It will die as its continously drained without getting charged.

Answer 2

Quiet down children, quiet down. Here's the drill. Your car's battery has but two purposes in life, and two only. One, to start the car. Two, to provide electrical power to the car for a short time when the engine is not running. At all other times, the alternator (or generator if you have an older car like a 1960s VW Bug) is driven by the engine and generates electricity to power all of the car's electrical systems as well as charge the battery. Under normal circumstances, the alternator provides more electricity than the car needs, and the excess goes into the battery to keep it charged. Under abnormal circumstances, like if you have a monster stereo and monster amps and monster off-road lights, the alternator can't produce enough electricity to keep up, and the battery kicks in. Do that for long enough and you will kill the battery. So to answer your questions, batteries DO die with the engine running and everything is on, including all the lights and your monster stereo and monster amps and billion-watt lights. But it's pretty unlikely because I think you're smart enough not to have all that junk. They also die if you run any of the electrical accessories with the engine off because there is no electricity charging the battery.

Answer 3

Batteries are made in several different operating modesThe 8 inch batteries will have less denser lead plates and a real hot acid mix.This acid mix gives higher cranking amps but because the plates have a less denser lead paste used in the production of the battery. The less denser the plates the less electric they save in the battery reserve .These batteries are lighter and lighten up the weight of the car (along with other components to get better milage) When buyuing a battery look for Delco or other batteries made by them and sold under names(Walmart for instance) Ask about thre reserve capacity on a battery and get the biggest one that wil fit your carIt should have at least 50-60 min. reserve capacity and your battery won't go dead as quick while listening to the radio or leaving a light on.Reserve Capacity also refers to how long your car can run on just the battery without an alternator Charging it as it also supplies electrical power to your accessories like radio,headlites so forth The higher the reserve also meansyoucan crank the engine a long tine trying to start it without going dead Hope this helps yu in your next purchase

Answer 4

Car batteries are designed to deliver a LOT of power for a short time in order to start your car. They are not designed to run your lights even for moderate lengths of time (3-4 hours). That is why the need to recharge the battery by means of your alternator while you are driving. Your lights, and all other electrics in the car are actually being run by the alternator while the car is running. the battery runs nothing while the car is running. Try to start a car too many times that doesn't want to start and it will die even quicker. It isn't reccommended to try starting your car more than three times in a row when it doesn't want to go or the battery will likely die.

Answer 5

Well, like any battery, with something left on drains the battery. With a car battery, and engine running there is a thing on the engine called an alternator. It helps to recharge the battery, and provide power to your lights, computer, for car to run properly, and for that favorite...STEREO:P So, as you can see, that how this stuff works.

Answer 6

They don't die when you drive because you only use the battery to START the car - after that, you run the car off your alternator.

But I feel your question - these batteries have an advertised life of, say, 60 months, and yet if you leave your lights on for one lousy night, you're F'd. I don't get that either.

Answer 7

The battery isn't renewed by the running engine. It needs food

Answer 8

that's why they die so fast,,if the car is running ,,it is charging it back up,,as it runs,,when it is not running it will kill a battery really fast,,because it don't charge any at all when its not running,,good luck,,i hope this help,s.

Answer 9

Indestructible Tactical LED Flashlight - http://FlashLight.uzaev.com/?fsxi

Answer 10

CAR BATTERIES DIE AND it will go dead just like a flashlight